Magnetic storage device which includes a three terminal magnetic sensor having a collector region electrically isolated from a slider body

ABSTRACT

In one illustrative example, a magnetic storage device includes a three terminal magnetic sensor having a collector region made of a semiconductor material, a base region, and an emitter region. An insulator layer is formed between the collector region and a slider body which carries the three terminal magnetic sensor. The insulator layer serves to reduce a capacitance otherwise present between the collector region and magnetic media at a magnetic field sensing plane of the three terminal magnetic sensor. Thus, the insulator layer electrically isolates the collector region from the slider body. The structure may be formed through use of a separation by implanting oxygen (SIMOX) technique or a wafer-bonding technique, as examples.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of and claims priority to a U.S.patent application entitled “Three Terminal Magnetic Sensor Having ACollector Region Electrically Isolated From A Carrier Substrate Body”having application Ser. No. 11/125,648 and a filing date of 10 May 2005,now U.S. Pat. No. 7,719,069 which is hereby incorporated herein byreference.

BACKGROUND

1. Field of the Technology

This present invention relates generally to magnetic storage deviceshaving three terminal magnetic sensors (TTMs) suitable for use inmagnetic heads, including spin valve transistors (SVTs), magnetic tunneltransistors (MTTs), or double junction structures.

2. Description of the Related Art

Magnetoresistive (MR) sensors have typically been used as read sensorsin hard disk drives. An MR sensor detects magnetic field signals throughthe resistance changes of a read element, fabricated of a magneticmaterial, as a function of the strength and direction of magnetic fluxbeing sensed by the read element. The conventional MR sensor, such asthat used as a MR read head for reading data in magnetic recording diskdrives, operates on the basis of the anisotropic magnetoresistive (AMR)effect of the bulk magnetic material, which is typically permalloy. Acomponent of the read element resistance varies as the square of thecosine of the angle between the magnetization direction in the readelement and the direction of sense current through the read element.Recorded data can be read from a magnetic medium, such as the disk in adisk drive, because the external field from the recorded magnetic medium(the signal field) causes a change in the direction of magnetization inthe read element, which causes a change in resistance of the readelement and a resulting change in the sensed current or voltage.

A three terminal magnetic sensor (TTM) of a magnetic head may comprise aspin valve transistor (SVT), for example, which is a vertical spininjection device having electrons injected over a barrier layer into afree layer. The electrons undergo spin-dependent scattering, and thosethat are only weakly scattered retain sufficient energy to traverse asecond barrier. The current over the second barrier is referred to asthe magneto-current. Conventional SVTs are constructed using atraditional three-terminal framework having an “emitter-base-collector”structure of a bipolar transistor. SVTs further include a spin valve(SV) on a metallic base region, whereby the collector current iscontrolled by the magnetic state of the base region using spin-dependentscattering. Although the TTM may involve an SVT where both barrierlayers are Schottky barriers, the TTM may alternatively incorporate amagnetic tunnel transistor (MTT) where one of the barrier layers is aSchottky barrier and the other barrier layer is a tunnel barrier, or adouble junction structure where both barrier layers are tunnel barriers.

The revolution in magnetic storage technology has been led byminiaturization of every component in the system, especially themechanical fly height. A slider may provide a fly height of less than 10nanometers, for example. In the prior art, the collector region of a TTMis typically formed as part of a slider body of the hard disk drive.Even though the slider body may be very small, the slider body is muchlarger than that needed as the collector region for TTM operation.

Based on these relative dimensions, it has been identified that aninherent capacitance between the magnetic media and the collectorregion/slider body for such small sliders (e.g. Femto sliders) is verylarge in light of a typical operating frequency of the hard disk drive.For example, the capacitance may be about 18 picofarads (pF) for typicaloperating frequencies of the hard disk drive of about 1 Gigahertz (Ghz).Such a large capacitance will unnecessarily reduce the signal from themagnetic media and introduce unnecessary noise into the circuit.

Accordingly, there is a need to solve these problems so that TTMs may besuitable for use in these and other devices.

SUMMARY

In one illustrative example, a magnetic storage device has a threeterminal magnetic sensor which includes a collector region made of asemiconductor material, a base region, and an emitter region. Aninsulator layer is formed between the collector region and a slider bodywhich carries the three terminal magnetic sensor. The insulator layerserves to reduce a capacitance between the collector region and magneticmedia at a magnetic field sensing plane of the three terminal magneticsensor. Thus, the insulator layer electrically isolates the collectorregion from the slider body. The structure may be formed through use ofa separation by implanting oxygen (SIMOX) technique or a wafer-bondingtechnique, as examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become more apparentto those skilled in the art after considering the following detaileddescription in connection with the accompanying drawings.

FIG. 1 is a cross-sectional view of a disk drive which may embody amagnetic head having a three terminal magnetic sensor (TTM) such as aspin valve transistor (SVT);

FIG. 2 is a top-down view of the disk drive of FIG. 1;

FIG. 3 is a perspective view of a typical TTM which has a collectorregion formed as part of a carrier substrate body;

FIG. 4 is a partial schematic representation of the TTM of FIG. 3, wherea relatively large capacitance exists between the collector region andmagnetic media;

FIG. 5 is a perspective view of a TTM of the present application, whichhas an insulator layer formed between its collector region and thecarrier substrate body so as to reduce the capacitance between thecollector region and the magnetic media; and

FIG. 6 is a flowchart which describes a method of forming the TTM of thepresent application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one illustrative example, a magnetic storage device has a threeterminal magnetic sensor which includes a collector region made of asemiconductor material, a base region, and an emitter region. Aninsulator layer is formed between the collector region and a slider bodywhich carries the three terminal magnetic sensor. The insulator layerserves to reduce a capacitance between the collector region and magneticmedia at a magnetic field sensing plane of the three terminal magneticsensor. Thus, the insulator layer electrically isolates the collectorregion from the slider body. The structure may be formed through use ofa separation by implanting oxygen (SIMOX) technique or a wafer-bondingtechnique, as examples.

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

FIG. 1 is a simplified block diagram of a conventional magneticrecording disk drive for use with a three terminal magnetic sensor (TTM)of a magnetic head. FIG. 2 is a top view of the disk drive of FIG. 1with the cover removed. Referring first to FIG. 1, there is illustratedin a sectional view a schematic of a conventional disk drive of the typeusing a TTM. The disk drive comprises a base 510 to which are secured adisk drive motor 512 and an actuator 514, and a cover 511. Base 510 andcover 511 provide a substantially sealed housing for the disk drive.Typically, there is a gasket 513 located between base 510 and cover 511and a small breather port (not shown) for equalizing pressure betweenthe interior of the disk drive and the outside environment. A magneticrecording disk 516 is connected to drive motor 512 by means of a hub 518to which it is attached for rotation by drive motor 512. A thinlubricant film 550 is maintained on the surface of disk 516. Aread/write head or transducer 525 is formed on the trailing end of acarrier, such as an air-bearing slider 520. Transducer 525 is aread/write head comprising an inductive write head portion and a readhead portion. Slider 520 is connected to actuator 514 by means of arigid arm 522 and a suspension 524. Suspension 524 provides a biasingforce which urges slider 520 onto the surface of the recording disk 516.During operation of the disk drive, drive motor 512 rotates disk 516 ata constant speed, and actuator 514, which is typically a linear orrotary voice coil motor (VCM), moves slider 520 generally radiallyacross the surface of disk 516 so that read/write head 525 may accessdifferent data tracks on disk 516.

FIG. 2 illustrates in better detail suspension 524 which provides aforce to slider 520 to urge it toward disk 516. Suspension 524 may be aconventional type of suspension, such as the well-known Watroussuspension, as described in U.S. Pat. No. 4,167,765. This type ofsuspension also provides a gimbaled attachment of the slider whichallows the slider to pitch and roll as it rides on the air bearingsurface. The data detected from disk 516 by transducer 525 is processedinto a data readback signal by signal amplification and processingcircuitry in an integrated circuit chip 515 located on arm 522. Thesignals from transducer 525 travel via a flex cable 517 to chip 515,which sends its output signals to the disk drive electronics (not shown)via cable 519.

In FIG. 3, a conventional three terminal magnetic sensor (TTM) 400 ofthe spin valve transistor (SVT) type is shown. Although described asincorporating an SVT (where both barrier layers are Schottky barriers),the TTM may alternatively incorporate a magnetic tunnel transistor (MTT)(where one of the barrier layers is a Schottky barrier and the otherbarrier layer is a tunnel barrier), or a double junction structure(where both barrier layers are tunnel barriers).

TTM 300 of FIG. 3 has a base region 15, a collector region 20 which isadjacent base region 15, an emitter region 5, and a barrier region 10which separates emitter region 5 from base region 15. Collector region20 may be a semiconductor substrate made of silicon (Si) or othersuitable material. Collector region 20 is formed as part of a sliderbody 22 (which is one type of carrier substrate body) of the disk drive.Base region 15 preferably includes at least one soft ferromagnetic (FM)material, such as nickel-iron (NiFe), cobalt-iron (CoFe), or cobalt(Co), as well as a very thin metal (e.g. gold) which is sandwiched inbetween the FM materials. Barrier layer 10 is a non-magnetic insulatingmaterial, preferably made of aluminum-oxide, which is generally lessthan 10 Angstroms (Å) in thickness.

As indicated in FIG. 3, a trackwidth W_(T) of the magnetic head isdefined by the dimension of emitter region 5, base region 15, andcollector region 20 along the y-axis, while a stripe height Hs of themagnetic head is defined by the dimension of emitter region 5 along thex-axis. A sensing plane 1020 of TTM 300 is defined along sides of baseregion 15, collector region 20, and emitter region 5. This sensing plane1020 is at an air bearing surface (ABS) when TTM 300 is embodied in amagnetic head.

A non-magnetic insulator layer 1012 is offset behind sensing plane 1020and adjacent collector region 20 and base region 15. Insulator layer1012 may be, for example, an oxide material such as alumina. An emitterlead 35, which may be embodied as a ferromagnetic (FM) shield for TTM300, is positioned in contact with emitter region 5 at sensing plane1020. Emitter lead 35 serves as the electrical connection for emitterregion 5 to an external lead (not visible in FIG. 3). A base lead 36 ispositioned in contact with base region 15 behind sensing plane 1020.Base lead 36 and a collector lead (not visible in FIG. 3) are preferablynot formed along sensing plane 1020. Note that additional or alternativeleads may be formed in the TTM, which has at least three leads.

TTM 300 allows hot electrons emitted from emitter region 5 to travelthrough to base region 15 to reach collector region 20, which collectsthe magnetocurrent (i.e. collects the electrons). In operation, thedevice acts as a hot spin electron filter whereby barrier region 10between emitter region 5 and base region 15 operates to selectivelyallow the hot electrons to pass on through to base region 15 and then onthrough collector region 20. When TTM 300 is not functioning, the deviceis in a known quiescent state. In this case, the magnetization of thefree layer which comprises all or part of base region 15 is parallel tothe ABS plane. The direction of this magnetization depends on thedirection of the magnetic field produced by a pinned layer (not visible)formed adjacent the free layer. The scattering of electrons within thefree layer is dependent upon the orientation of the magnetization withinthe free layer. For example, if the magnetization is pointing in theparallel direction relative to the pinned layer (i.e. parallel to theABS plane), then the electrons are not scattered as much as compared tothe case where the free layer is antiparallel relative to the pinnedlayer. The performance of the device may be different depending upon therelative configuration of emitter region 5, the free layer, and the hardbias layer.

To further illustrate operation, FIG. 4 is provided to show a partialschematic representation of the TTM 300 (e.g. an SVT) of FIG. 3. Thesemiconductors and magnetic materials used in TTM 300 may include ann-type silicon (Si) material for emitter 5 and collector 20, and aNi₈₀Fe₂₀/Au/Co spin valve for base region 15. Energy barriers, alsoreferred to as Schottky barriers, are formed at the junctions betweenmetal base 15 and the semiconductors. It is desirable to obtain a highquality energy barrier at these junctions with good rectifying behavior.Therefore, thin layers of materials (e.g. platinum and gold) areoftentimes used at the emitter 5 and collector 20, respectively.Moreover, these thin layers separate the magnetic layers from thesemiconductor materials.

A TTM operates when current is introduced between emitter region 5 andbase region 15, denoted as I_(E) in FIG. 4. This occurs when electronsare injected over the energy barrier and into base region 15 by biasingthe emitter such that the electrons are traveling perpendicular to thelayers of the spin valve. Because the electrons are injected over theenergy barrier, they enter base region 15 as non-equilibrium hotelectrons, whereby the hot-electron energy is typically in the range of0.5 and 1.0 eV depending upon the selection of the metal/semiconductorcombination. The energy and momentum distribution of the hot electronschange as the electrons move through base region 15 and are subjected toinelastic and elastic scattering. As such, electrons are prevented fromentering collector region 20 if their energy is insufficient to overcomethe energy barrier at the collector side. Moreover, the hot-electronmomentum must match with the available states in the collectorsemiconductor to allow for the electrons to enter collector region 20.The collector current I_(C), which indicates the fraction of electronscollected in collector region 20, is dependent upon the scattering inbase region 15 which is spin-dependent when base region 15 containsmagnetic materials. Furthermore, an external applied magnetic fieldcontrols the total scattering rate which may, for example, change therelative magnetic alignment of the two ferromagnetic layers of the spinvalve. The magnetocurrent (MC), which is the magnetic response of theTTM, can be represented by the change in collector current normalized tothe minimum value as provided by the following formula: MC=[I^(P)_(C)−I^(AP) _(C)]/I^(AP) _(C), where P and AP indicate the parallel andantiparallel state of the spin valve, respectively.

The revolution in magnetic storage technology has been led byminiaturization of every component in the system, including the sliderbody. For example, sliders have been reduced in size to Nano sliders(early 1990's), to Pico sliders (1997), and to Femto sliders (2003)which represents the current state of the art. Typical dimensions of aFemto slider may be 700 μm (width)×230 μm (height)×850 μm (depth). Whenthe size of the slider is reduced, its “fly height” is accordinglyreduced. A Femto slider may have a fly height of about 3 nanometers, forexample.

As shown in FIG. 3, collector region 20 is formed as part of slider body22. Even though slider body 22 may be very small (e.g. less than 1 mm³),slider body 22 is much larger than that needed as collector region 20for TTM operation. Based on these relative dimensions, it has beenidentified that an inherent capacitance 312 (see FIG. 4) betweenmagnetic media 310 and collector region 20 for such small sliders (e.g.Femto sliders) is very large in view of a typical operating frequency ofthe disk drive. For example, the capacitance may be about 18 picofarads(pF) for typical operating frequencies of the hard disk drive of about 1Gigahertz (Ghz). Such a large capacitance 312 will unnecessarily reducethe signal from the magnetic media 310 and introduce unnecessary noiseinto the circuit.

FIG. 5 is a perspective view of a three terminal magnetic sensor (TTM)device 500 of the present application. TTM device 500 is the same asthat shown and described in relation to FIGS. 3-4, except that it doesnot exhibit the problems associated therewith due to structuralmodifications which will now be described.

To eliminate or mitigate the problem of existing TTMs, TTM device 500has an insulator layer 24 formed between its collector region 30 and itsslider body 32. Insulator layer 24 serves to electrically isolate sliderbody 32 from collector region 30, to thereby reduce or effectivelyeliminate the large capacitance (e.g. capacitance 312 of FIG. 4)otherwise present between collector region 30 and the magnetic media.Slider body 32 still serves as a substrate to carry TTM device 500 formagnetic storage purposes.

Preferably, slider body 32 is made of the same materials as collectorregion 30. These materials are preferably semiconductor materials, whichmay be or include silicon (Si) materials. Alternatively, slider body 32and collector region 30 are made from materials different from eachother. Insulator layer 24 may be made of any suitable electricallyinsulating materials, such as an oxide. For example, insulator layer 24may be made from aluminum-oxide (alumina or Al₂O₃) or silicon dioxide(SiO₂).

The thicknesses of the materials and regions may vary depending on thedesign requirements, the size of the TTM, and the size of the sliderbody. In one embodiment, slider body 32 is a Femto slider, TTM 500 hastrackwidth dimensions between 10 nm and 100 nm, and the fly height isbetween about 1 nm and 10 nm. In this case, insulator layer 24 is formedwith a thickness of between about 10 nm and 10,000 nm, and collectorregion 30 is formed with a thickness of between about 1 nm and 1000 nm.

Thus, the TTM device 500 of the present application includes collectorregion 30 made of a semiconductor material, base region 15, and emitterregion 5. Insulator layer 24 is formed between collector region 30 andslider body 32 which carries the TTM device 500, which electricallyisolates collector region 30 from slider body 32. This reduces oreffectively eliminates a capacitance between collector region 30 andmagnetic media, so that magnetic signals may be adequately sensed fromthe magnetic media at the appropriate operating frequencies (e.g. 1Gigahertz or greater).

There are several conventional processes utilized for fabricating suchTTMs. These processes typically employ lithography, planarization, RIEetching, and other well-known techniques. Preferably, the TTM devicestructures of the present application are formed through the further useof a “separation by implanting oxygen” (SIMOX) technique. Alternatively,the TTM device structures of the present application are formed throughthe further use of a wafer-bonding technique. General SIMOX andwafer-bonding techniques are known in the field of semiconductorfabrication, but are specifically utilized and tailored herein toachieve the desired structural and functional results.

FIG. 6 is a flowchart which describes a general method of forming TTMdevice 500 of the present application. Beginning at a start block 602 ofFIG. 6, a carrier substrate body comprising a semiconductor material isprovided (step 604 of FIG. 6). Next, an insulator layer is formed inbetween the carrier substrate body and a collector region of the TTMdevice (step 606 of FIG. 6). A base region of the TTM device is thenformed over the collector region of the TTM device (step 608 of FIG. 6).An emitter region is then formed over the base region of the TTM device(step 610 of FIG. 6). The method corresponding to the steps described inthe flowchart of FIG. 6 ends at an end block 612, but additionalprocessing steps may be subsequently performed to complete themanufacture of the TTM device.

With use of the SIMOX technique, in particular, a slider body made ofsemiconductor material (e.g. silicon) is first provided. A high dose ofoxygen ions are implanted into the slider body over a top surface whichwill later form part of the collector region. The implant energy, whichmay be between about 150-300 keV, serves to locate a peak of theoxygen-implantation beneath the top surface. The dose of oxygen ions maybe on the order of 2×10¹⁸/cm². The slider body is then annealed. Theannealing process may, for example, be performed in N₂ for 3-5 hours ata high temperature (e.g. 1300-1350° C.). The annealing process forms acontinuous buried-oxide (BOX) layer within the slider body with thecollector region being formed above this BOX layer. The thickness of thecollector region may be varied by subsequently depositing an epitaxialsilicon layer or by etching. Note that nitrogen may be used in place ofoxygen for this method.

With use of the wafer-bonding technique, in particular, two wafers madeof a semiconductor material (e.g. silicon) are first provided. A surfaceportion of at least one of the wafers is oxidized. The two wafers arethen positioned together and thermally bonded with the oxidized portionof the one wafer facing the other wafer. The bonding temperature mayvary between about 400° C.-1200° C. The oxidized portion forms theinsulator layer between the slider body and the collector region. It ispreferred that the bonding or wafer insulation occurs before devicefabrication due to the high thermal budget of SOI-like wafers. Thethermal budget for most magnetic sensors is below 400° C. To prepare forthe bonding, the wafers may be rinsed (e.g. with water) under a lowspeed rotation and then dried with a heat lamp under a high speedrotation. After the bonding, the wafer unit may be thinned through athinning process and/or a splitting process. In one splitting processtechnique, a high dose of oxygen ions are implanted into the oxidizedwafer, the depth of which defines the split which occurs during apost-bonding annealing process. Thus, at least part of one of the wafersis utilized as the slider body and at least part of the other wafer isutilized as the collector region. Using the wafer-bonding technique,insulator layers of greater thickness than that achieved through use ofthe SIMOX technique are possible.

Regardless of which technique is utilized, after the slider body isformed with the insulator layer between it and the collector region, asensor stack structure is then formed. The sensor stack structureincludes at least a base region which is formed below an emitter region.Thus, the further steps of the method include forming, over thecollector region, a base region of the three terminal magnetic sensordevice; and forming, over the base region, an emitter region of thethree terminal magnetic sensor device. These may be formed using typicaldeposition and lithography techniques known in the art.

Final Comments. As described herein, a three terminal magnetic sensorincludes a collector region made of a semiconductor material, a baseregion, and an emitter region. An insulator layer is formed between thecollector region and a carrier substrate body which carries the threeterminal magnetic sensor. The insulator layer serves to reduce acapacitance between the collector region and magnetic media at amagnetic field sensing plane of the three terminal magnetic sensor.Thus, the insulator layer electrically isolates the collector regionfrom the carrier substrate body. The base region and the emitter regionmay be similarly isolated. The structure may be formed through use of aseparation by implanting oxygen (SIMOX) technique or a wafer-bondingtechnique, as examples.

A magnetic storage device of the present application includes a sliderbody, a magnetic head carried on the slider body, and a read headportion of the magnetic head which includes a three terminal magneticsensor for reading magnetic signals from magnetic media at a magneticfield sensing plane. The three terminal magnetic sensor includes acollector region made of a semiconductor material, a base region, and anemitter region. An insulator layer is formed between the collectorregion and the slider body so as to reduce a capacitance between thecollector region and magnetic media at an air bearing surface (ABS) ofthe magnetic head. Thus, the insulator layer electrically isolates thecollector region from the slider body.

A method of forming a three terminal magnetic sensor device of thepresent application includes the steps of providing a carrier substratebody comprising a semiconductor material; forming an insulator layer inbetween the carrier substrate body and a collector region of the threeterminal magnetic sensor device; forming, over the collector region, abase region of the three terminal magnetic sensor device; and forming,over the base region, an emitter region of the three terminal magneticsensor device. The act of forming the insulator layer in between thecarrier substrate body and the collector region may comprise the furtheracts of performing an oxygen or nitrogen ion implantation over a surfaceof the carrier substrate body and then annealing the carrier substratebody. Thus, the act of forming the insulator layer in between thecarrier substrate body and the collector region may comprise aseparation by implanting oxygen (SIMOX) technique where the insulatorlayer comprises a continuous buried-oxide (BOX) layer within the carriersubstrate body. Alternatively, the act of forming the insulator layer inbetween the carrier substrate body and the collector region may comprisethe further act of performing a wafer bonding process. Here, the act offorming the insulator layer in between the carrier substrate body andthe collector region may comprise bonding a first wafer over a secondwafer which has at least part of the insulator layer.

It is to be understood that the above is merely a description ofpreferred embodiments of the invention and that various changes,alterations, and variations may be made without departing from the truespirit and scope of the invention as set for in the appended claims. Forexample, although the TTM is described as a three-leaded device, it mayactually have three or more leads. Few if any of the terms or phrases inthe specification and claims have been given any special particularmeaning different from the plain language meaning to those ordinarilyskilled in the art, and therefore the specification is not to be used todefine terms in an unduly narrow sense.

1. A magnetic storage device, comprising: a slider body made of asemiconductor material, the slider body including a top semiconductorlayer and a bottom semiconductor layer; a magnetic head carried on theslider body; a read head portion of the magnetic head which includes athree terminal magnetic sensor having three terminals; the threeterminal magnetic sensor being configured for reading, at a magneticfield sensing plane, magnetic signals from magnetic media of themagnetic storage device; the three terminal magnetic sensor including: abase region; an emitter region; a collector region which is the topsemiconductor layer of the slider body and composed of the semiconductormaterial of the slider body; the base region comprising magneticmaterials and being formed in between the emitter and the collectorregion; a base lead in contact with the magnetic materials of the baseregion; an emitter lead in contact with the emitter region; a collectorlead in contact with the top semiconductor layer of the slider body; thebase lead, the emitter lead, and the collector lead forming the threeterminals of the three terminal magnetic sensor; a first barrier regionformed between the base region and the emitter region; a second barrierregion formed between the base region and the collector region; and aninsulator layer which separates the top semiconductor layer of theslider body from the bottom semiconductor layer of the slider body, forelectrically isolating at the magnetic field sensing plane the collectorregion from the bottom semiconductor layer of the slider body, so as toeffectively eliminate a capacitance otherwise present between thecollector region and the magnetic media.
 2. The magnetic storage deviceof claim 1, wherein the slider body comprises a wafer-bonded structurehaving a first slider body portion that is wafer-bonded together with asecond slider body portion, and the insulator layer is an oxidizedsurface of the first slider body portion that is wafer-bonded togetherwith the second slider body portion, where the oxidized surface facesthe second slider body portion.
 3. The magnetic storage device of claim1, wherein the slider body has dimensions of less than 1 mm³ and a flyheight of no greater than 3 nanometers with respect to the magneticmedia.
 4. The magnetic storage device of claim 1, wherein the threeterminal magnetic sensor is for reading magnetic signals from magneticmedia of the magnetic storage device at operating frequencies of 1Gigahertz or greater.
 5. The magnetic storage device of claim 1, whereinthe emitter region is configured to receive electrons which travelperpendicular to the planes of the base, the emitter, and the collectorregions.
 6. The magnetic storage device of claim 1, wherein theinsulator layer comprises silicon-dioxide.
 7. The magnetic storagedevice of claim 1, wherein the insulator layer comprises an oxide. 8.The magnetic storage device of claim 1, further comprising a disk drive.9. The magnetic storage device of claim 1, wherein the three terminalmagnetic sensor comprises a magnetic tunnel junction structure.
 10. Themagnetic storage device of claim 1, wherein the three terminal magneticsensor comprises a double tunnel structure.